A part-finished aluminium mushroom shape with a hollow stalk to take a fine-pitch M12 thread. This is help in a Gerardi milling vice and it has watery coolant beads splashed on the vice and part

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   Neil G4DBN (g4dbn@mastodon.radio)'s status on Wednesday, 01-May-2024 13:47:17 JST Neil G4DBN

   When I'm designing a Cassegrain antenna for mmWave radio, the main dish is a parabola, but the deep ones from Edmund Optics are very hard to illuminate because they have a focal length to diameter ratio of 0.25, which is WAAAAAY less than most dishes. Solution is to put a hyperboloidal subreflector with its rear focus coincident with the prime focus of the parabola, and the front focus of the hyp is where you put the feedhorn. I made the rear so it can take a very fine adjustment thread